Which condition indicates the presence of frost on the suction line?

Which condition indicates the presence of frost on the suction line?

• A. The line temperature is above the dew point
• B. The line temperature is below the dew point and below 32°F
• C. The line temperature is equal to ambient
• D. The line is warm to touch

Answer: (B)

Frost on a suction line happens when the surface is cold enough to freeze moisture from the air. The dew point is the temperature at which air becomes saturated and moisture starts to condense on a surface. If that surface is below freezing, the condensed moisture freezes, forming frost. So the condition that produces frost is when the line temperature is below both the dew point and 32°F. If the line is only below the dew point but above freezing, you’d get dew, not frost. A line at ambient temperature or warm to the touch won’t frost.

Frost on a suction line happens when the surface is cold enough to freeze moisture from the air. The dew point is the temperature at which air becomes saturated and moisture starts to condense on a surface. If that surface is below freezing, the condensed moisture freezes, forming frost. So the condition that produces frost is when the line temperature is below both the dew point and 32°F. If the line is only below the dew point but above freezing, you’d get dew, not frost. A line at ambient temperature or warm to the touch won’t frost.